0.64BaTi4O9-0.36BaEu2Ti4O12/BaTi4O9纤维复合陶瓷的介电性研究

对0.64BaTi4O9-0.36BaEu2Ti4O12/BaTi4O9纤维复合陶瓷新材料的相组成、介电性能和样品表面原子的化学组成及Ti元素的价态变化进行了研究.研究结果表明该复合陶瓷新材料只由BaTi4O9和BaEu2Ti4O12两相组成.加入BaTi4O9纤维后,复合陶瓷材料中Ti3+离子和Ti2+离子的含量降低,氧元素的含量提高,并且BaTi4O9纤维对该材料体系的介质损耗有明显的改善作用,其中含10vol%BaTi4O9纤维的BET10试样的性能最佳,其εr=55,tgδ=3×10-4(在1MHz条件下).     

BaTi4O9微波介质陶瓷制备及低温烧结研究进展

微波介质陶瓷作为现代移动通讯中的关键基础材料,以其优异的介电性能已成为现代微波通讯技术的研究重点之一,而BaO-TiO2体系中的BaTi4O9微波介质陶瓷由于具有微波介电性能优异、制备工艺简单以及成本低等优点,已经成为微波介质陶瓷研究领域的热点.从BaTi4O9微波介质陶瓷的结构与性能入手,介绍了BaTi4O9陶瓷的制备工艺、方法及其在器件方面的应用,概述了BaTi4O9微波介质陶瓷在低温烧结方面的研究进展.     

BaO-TiO2系纤维的合成及BaT4O9纤维复合陶瓷的研究

摘要以水热法合成出BaTi4O9和BaTi5O11两种新型的功能陶瓷纤维,制备了三个体系的BaTi4O9纤维复合陶 瓷新材料,并对其组织结构、介电性能和室温断裂行为进行了研究.论文取得了如下创造性研究成果:(1)合成出以 BaTi4O9和BaTi5O11为主晶相的纤维新材料;对原料K2Ti4O9纤维的形成机制进行了探讨;同时,对中间产物水合二氧 化钛纤维的相变过程进行了研究;(2)成功地制备出BaTi4O9(f)/(0.64BaTi4O9+0.36BaPr2Ti4O12)(简称BPT系列) 和BaTi4O9(f)/()(0.64BaTi4O9+0.36BaEu2Ti4O12)(简称BET系列)两个系列复合陶瓷材料,系统研究了BaTi4O9纤 维的加入量对介电性能的影响,结果表明,含10vol%BaTi4O9纤维的BPT和BET试样具有良好的综合介电性能;(3) 对BaTi4O9纤维和复合陶瓷的组织结构进行了系统研究,揭示了介电性能变化的结构基础,对进一步开发新的相应系 列的微波介质陶瓷材料有重要的参考价值;(4)由纯BaTi4O9纤维制成的试样具有较好的烧结性和介电特性. 关键词微波介质陶瓷纤维复合陶瓷 BaTi4O9纤维介电性能 导师:周玉教授和王福平教授答辩时间:2000-10-19 通讯地址:哈尔滨工业大学2045信箱     

Sol-gel法制备BaTiO_3、BaTi_2O_5和BaTi_4O_9粉末

采用Sol-gel法合成了BaTiO3、BaTi2O5和BaTi4O9粉末,利用XRD和SEM研究了它们的晶相和微观结构。在较低温度烧结得到的粉末都存在一定量的杂相,随着烧结温度的升高,杂相逐渐消失。在1000℃以上温度烧结,可以得到单相BaTiO3和BaTi2O5粉末,而单相BaTi4O9粉末则在1300℃以上温度烧结得到。随着n(Ba)/n(Ti)减小,所得单相的烧结温度逐渐升高。随着烧结温度的升高,BaTiO3、BaTi2O5和BaTi4O9粉末的晶粒逐渐长大。800℃以上温度烧结得到的四方BaTiO3钙钛矿相粉末主要由方形和圆形的晶粒组成;1100℃烧结得到的单斜BaTi2O5相粉末主要由近似菱形的晶粒组成;在1200℃烧结得到的正交BaTi4O9相粉末基本由长形的晶粒组成。     

四钛酸钡纤维陶瓷的制备及介电性研究

首次制备了BaTi4O9纤维陶瓷新材料。利用XRD分析烧结前后试样的相组分变化并在SEM和TEM下观察分析试样的微观结构。初步研究了材料的介电性能。     

BaTi4O9微波介质陶瓷的低温烧结

研究液相多元添加对BaTi4O9微波介质陶瓷的烧结和介电性能的影响.通过添加(CuO和V2O5)烧结助剂来达到降低烧结温度的效果,并且使其保持较好的微波、高频性能.实验结果表明在添加合适的烧结助剂下,烧结温度为1180℃时,BaTi4O9微波介质陶瓷在1MHz下的介电性能ε=41.2,tgδ=5,τ=82×10-6/℃.基本保持了良好的介电性能.     

聚合物分解法合成BaSm 2Ti 4 O 12

以BaCO3、Sm（NO3）3及Ti（OC4H9）4为原料，采用柠檬酸盐前驱体法制备BaSm2 Ti4O12并与草酸盐共沉淀法制备BaSm2 Ti4O12粉体过程作了比较．结果发现，利用聚合物分解法，可以在1000℃的较低温度下得到单相结晶的BaSm2 Ti4O12，而草酸盐沉淀法则需要1300℃的高温才能合成纯的BaSm2 Ti4O12相．研究表明，这两种液相法所需合成温度相差很大，是由于不同的相演化过程及反应步骤所致．在共沉淀法中，当煅烧前驱体时，中间相Sm2 Ti2O7与BaTi4O9和BaTiO3反应生成BaSm2 Ti4O12相，其过程与固相法相类似．而在聚合物分解法中，前驱体在热分解过程中生成BaTi2O5相，导致了与固相过程完全不同的反应机制，促进了BaSm2 Ti4O12相的形成．     

水热法制备BaTi4O9纤维

通过水热法首次制备了微波介质材料－－ＢａＴｉ４Ｏ９的纤维体。对由此方法制得的钡钛纤维前驱全在７５０－１０００℃温区范围内进行了煅烧合成实验，通过Ｘ衍射定向分析表明：在７５０℃保温２小时的合成条件下，开始出现ＢａＴｉ４Ｏ９；在１０００℃保温２小时的合成条件下，可获得ＢａＴｉ４Ｏ９为主晶相的纤维。     

BaTinO2n+1光催化性能和结构关系的研究

光催化剂BaTinP2n＋1（n=1，2和4）粉末是通过sol—gel法制得的聚合物前驱体在800℃下烧制而成．利用XRD粉末衍射和UV—Vis吸收光谱表征样品的物相和吸收光谱特性．在样品的光催化活性测试中，采取甲基橙作为染料光降解的模型，研究了BaTiO3、BaTi2O5和BaTi4O9在各种酸性条件下对甲基橙溶液的降解效率，并初步探讨了其光催化性能差异的影响机制．实验表明，在相同的酸性条件下，三种钛酸钡BaTinP2n＋1（n=1，2和4）的光催化活性都随n的增大而增强，即BaTiO3〈BaTi2O5〈BaTi4O9．引入堆积率（定义为单位晶胞内所有组成离子的体积占整个晶胞体积的百分比）的概念，堆积率越小，则表明材料晶体结构越开放．利用结构开放度的概念模型可以很好地解释光催化活性的差异，即在这三种材料中，结构越开放，光催化性能越好．     

温度对Mg4Nb2O9合成的影响

Mg4Nb2O9具有与α-Al2O3相同的刚玉型晶体结构,可望成为取代氧化铝陶瓷的新一代高Q值基板陶瓷.在900～1400℃温度范围内,合成了Mg4Nb2O9化合物,采用X射线粉末衍射法进行了相结构分析.结果表明,生成物中含有Mg4Nb2O9、Mg4Nb2O6和MgO三种物相,主晶相是Mg4Nb2O9;在900～1300℃温度范围内,随着温度的升高,MgNb2O6和MgO反应生成Mg4Nb2O9相,主晶相含量线性增加,但在1300℃以上,主晶相含量随温度的升高而减小;Mg4Nb2O9相的最佳合成温度为1300℃.这些结果对研究开发Mg4Nb2O9微波基板材料有着重要的意义.     

Preparation and characterization of SiO2-pillared H2Ti4O9 and its photocatalytic activity for methylene blue degradation

SiO(2) pillared layered titanate (SiO(2)-H(2)Ti(4)O(9)) was prepared via intercalating organosilanes into the interlayers of the layered K(2)Ti(4)O(9) followed by calcination at 500 degrees C. The resulting materials were characterized using XRD, N(2) adsorption-desorption isotherms, UV-vis spectra, IR spectroscopy and Raman spectroscopy. The photocatalytic activity of SiO(2)-H(2)Ti(4)O(9) was evaluated by photocatalytic degradation of aqueous methylene blue dye (MB). XRD and specific surface area results showed that SiO(2)-H(2)Ti(4)O(9) had an interlayer distance of 1.45 nm and a specific surface area of 148 m(2)g(-1). UV-vis absorption spectrum of SiO(2)-H(2)Ti(4)O(9) showed a red shift, indicative of a narrower band gap compared to K(2)Ti(4)O(9). In addition, SiO(2)-H(2)Ti(4)O(9) showed higher MB adsorption capacity compared to H(2)Ti(4)O(9) and K(2)Ti(4)O(9). MB photodegradation over H(2)Ti(4)O(9), K(2)Ti(4)O(9) and SiO(2)-K(2)Ti(4)O(9) followed zero-order kinetics under our experimental conditions, and the photocatalytic activity of SiO(2)-H(2)Ti(4)O(9) was found to be three times higher than that of K(2)Ti(4)O(9), which could be attributed to the increase of interlayer space and specific surface area of SiO(2)-pillared layered titanate.     

Dielectric properties of BaTi4O9 single crystals

The barium tetratitanate (BaTi₄O₉) single crystals grown in a nitrogen gas by the floating zone method was characterized by dielectric property in the frequency range 1 kHz to 1 MHz. The as-grown crystals had an electric behaviour such as shown by a semiconductor. When the crystals were annealed at 1300° C for 5 h in air, the dielectric constant was independent of the frequencies and was anisotropic, and theQ-value became higher than that of the grown crystals. Further, from electron spin resonance measurements it was found that the as-grown crystals contained the Ti³⁺ ion. This seems to suggest that the electrical conductivity of the as-grown crystals is due to the Ti³⁺-Ti⁴⁺ hopping mechanism.     

Ti4+取代Zn2+、Nb5+对Bi2O3-ZnO-Nb2O5系介质材料结构和性能的影响

研究了Ti4 取代Zn2 ,Nb5 对Bi2O3-ZnO-Nb2O5系介质材料结构和性能的影响，研究表明，少量替代对于材料的结构和性能没有太大的影响；随着替代量的增加，相结构中出现正交Bi4Ti3O12相；微观形貌中出现棒晶，介电常数逐渐增大，温度系数逐渐向负温度系数方向移动，适量Ti4 替代可以获得性能很好的NP0介质材料。     

Properties of Mn-doped BaTi4O9-ZnO-Ta2O5 ceramics

In Part I, the reaction sequence, microstructural analysis and microwave dielectric properties of manganese-doped BaTi₄O₉ + ZnO + Ta₂O₅ ceramics are discussed. This composition undergoes complex intermediate reactions during calcination. However, the final crystal phases after the sintering process were identical regardless of calcination temperature. Meanwhile, different calcination temperatures affect the relative volume fractions of the BaZn₂Ti₄O₁₁ phase and result in variations in T _f values. To analyse the microstructure, SEM, TEM and EDS analysis were performed. Mn dopants greatly enhanced the Q factor, up to 11000 at 4.5 GHz, whereas undoped ceramics indicated a high loss, probably due to the formation of Ti³⁺ during sintering in air.     

New high permittivity and low loss ceramics in the BaO–TiO2–Nb2O5 composition

New dielectric ceramics with formula BaTi3Nb4O17 and Ba6Ti14Nb2O39 have been prepared and characterized. BaTi3Nb4O17 was densified to 92% of TD after firing at 1310 °C for 4 h. However, Ba6Ti14Nb2O39 fired under optimized conditions (1260 °C for 4 h) showed only 85% TD together with secondary phase. The crystal system of both of the compositions is orthorhombic. The BaTi3Nb4O17 has r56, Qu2100 (at 4.402 GHz), f+86 p.p.m. K-1 and Ba6Ti14Nb2O39 as r50, Qu650 (4.359 GHz) and f+165 p.p.m. K-1. © 1998 Kluwer Academic Publishers     

Sr掺杂BaTi2O5单晶的制备与介电性能研究

采用悬浮区熔技术制备了一种Sr掺杂的二钛酸钡（BaTi2O5）单晶（Ba1-xSrxTi2O5,x=O-0．03）,重点研究了Sr掺杂量对其结构和介电性能的影响。结果表明：成功制备出物相单一、沿b轴方向生长的Ba1-xSkTi2O5单晶;适量Sr掺杂能有效改善Ba1-xSkTi2O5单晶的介电性能,其居里温度随Sr掺杂量的增加稍有降低,而介电常数极大值则呈现先增大后减小的趋势,在Sr掺杂量X=0．01时达到最大值42190。     

Nb掺杂Bi4Ti3O12层状结构铁电陶瓷的电行为特性研究

采用固相烧结工艺制备了Nb⁵⁺掺杂的Bi₄Ti₃O₁₂层状结构铁电陶瓷.运用XRD 和AFM对Bi₄Ti_3-xNb_xO_12+x/2材料的微观结构进行表征,发现所制备的陶瓷均具有单一的正交相结构,抛光热腐蚀表面晶粒的显微形貌表现为随机排列的棒状结构.通过对材料直流电导率与温度关系的Arrhenius拟合,分析丁Bi₄Ti_3-xNb_xO_12+x/2的导电机理. Nb⁵⁺掺杂提高了材料的介电常数,但居里温度随掺杂含量的增加呈线性下降趋势.DSC结果显示Bi₄Ti_3-xNb_xO_12+x/2材料在居里温度处经历了一级铁电相变.样品的铁电性能测试结果表明, Nb⁵⁺掺杂Bi₄Ti₃O₁₂提高了材料的剩余极化Pr,这主要是由于^_Nb5+取代Ti⁴⁺大大降低了材料中氧空位的浓度,使得氧空位对畴的钉扎作用减弱的缘故.     

Ti(OC4H9)4-MAPS体系溶胶-凝胶转变研究

研究了Ｔｉ（ＯＣ４Ｈ９）４－ＭＡＰＳ体系中Ｔｉ（ＯＣ４Ｈ９）４、ＭＡＰＳ、Ｃ２Ｈ５ＯＨ、Ｈ２Ｏ４个原料组分对聚钛硅氧烷产转变规律的影响。结果表明,增大水和Ｔｉ（ＯＣ４Ｈ９）４的用量或降低ＭＡＰＳ和Ｃ２Ｈ５ＯＨ的用量,菜成凝胶;反之,则易形成溶胶。